A Phase 3 interventional study of Proton Therapy in Breast Cancer, sponsored by Proton Collaborative Group. Recruiting at 9 sites in United States. Open to female participants aged 19 Years and older. Per ClinicalTrials.gov, last updated 2026-09-29.
Sponsored by Proton Collaborative Group · Phase 3, Interventional, and Treatment
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The purpose of this research study is to learn more about the effects of using proton radiation therapy delivered over a shorter course of treatment (3 weeks) compared with a longer, standard course of treatment (5 weeks) for women with breast cancer who require radiotherapy to the breast/chest wall and regional lymph nodes.
This study is being done to see if comprehensive regional nodal radiation therapy to the breast or chest wall and regional lymph node area using proton therapy delivered with a hypofractionated approach (less treatment days) will result in rates of treatment related skin and soft tissue side effects that are non-inferior compared to conventionally fractionated proton radiotherapy regimens.
14,832 studies on the registry are indexed under Breast Neoplasms; 3,320 are open to participants now.
This study's planned enrollment of 276 is above the median of 72 across 10,903 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →Proton Collaborative Group is the lead sponsor of 10 studies on the registry; 6 are open to participants now.
Counted across the registry records on this site, refreshed daily.
The criteria were revised on the registry on Sep 29, 2026. See what changed
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
50-50.4 Gy (RBE) in 25-28 daily fractions of 1.8-2.0 Gy (RBE) plus a Tumor Bed Boost (for intact breast) of 10 Gy (RBE) in 4-5 daily fractions of 2-2.5 Gy (RBE) \*\*Additional boost of 10-20 Gy (RBE) in 2-2.5 Gy (RBE) fractions to clinically involved lymph nodes or chest wall/scar allowed at the treating physician's discretion\*\*
Radiation: Proton Therapy
40.05 Gy (RBE) in 15 daily fractions of 2.67 Gy (RBE) plus a Tumor Bed Boost (for intact breast) of 10 Gy (RBE) in 4-5 daily fractions of 2-2.5 Gy (RBE) \*\*Additional boost of 10-20 Gy (RBE) in 2-2.5 Gy (RBE) fractions to clinically involved lymph nodes or chest wall/scar allowed at the treating physician's discretion\*\*
Radiation: Proton Therapy
Pencil Beam Scanning (PBS)
To determine if the rate of grade ≥3 treatment-related skin and soft tissue toxicities with comprehensive nodal irradiation for breast cancer using hypofractionated PBS proton therapy is non-inferior to conventionally-fractionated proton radiotherapy
This study will investigate if adjuvant comprehensive regional nodal radiotherapy to the breast or chest wall and regional lymph nodes including the axilla (levels I-III), supraclavicular (SCV), and internal mammary (IMN) lymph nodes using pencil beam scanning proton therapy delivered with a hypofractionated regimen results in rates of acute and late grade 3 or worse treatment-related skin and soft tissue toxicities that are non-inferior compared with rates in pencil beam scanning proton therapy using conventionally fractionated regimens.
Time frame: 2 years after radiation therapy
To determine the rate of any grade ≥3 treatment-related adverse events
Time frame: 2, 5, and 10 years after radiation therapy
To determine local recurrence rates
Time frame: 2, 5, and 10 years after radiation therapy
To determine regional recurrence rates
Time frame: 2, 5, and 10 years after radiation therapy
To determine distant recurrence rates
Time frame: 2, 5, and 10 years after radiation therapy
To determine breast cancer-specific survival
Time frame: 2, 5, and 10 years after radiation therapy
To determine overall survival
Time frame: 2, 5, and 10 years after radiation therapy
To assess patient-reported quality of life
FACT-B questionnaire
Time frame: 2, 5, and 10 years after radiation therapy
To assess patient-reported quality of life
BREAST-Q questionnaire
Time frame: 2, 5, and 10 years after radiation therapy
To assess physician-reported cosmetic outcomes
Physician reported cosmesis form
Time frame: 2, 5, and 10 years after radiation therapy
To correlate dosimetric parameters with acute and late adverse events for the development of model dose constraints for comprehensive nodal irradiation for breast cancer using a moderately hypofractionated regimen with PBS-PT
Time frame: 2, 5, and 10 years after radiation therapy
Plan to share: No
No publications or documents are linked to this record.
Started Mar 2024 (actual). Primary completion is estimated for Feb 2038, 167 months after the start.
Of 328 non-industry phase 3 interventional studies under Breast Neoplasms, half reached primary completion within 79 months of starting (the median), counting those still running; a quarter within 50 and three quarters within 127. This study's planned 167 months is above that.
Counting every sponsor, half of 600 studies reached it within 59 months; a quarter within 36 and three quarters within 96.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Proton Collaborative Group